It wasn't long ago, just 2008, when the stores stayed on the Friday side of the line. Target opened at 6 a.m., while most like K-Mart, Sears, and Walmart opened at 5 a.m. But in 2009, Toys 'R Us crossed the midnight threshold, and the race was on.

Now, four years later, most major retailers will open their doors at 8 p.m. or 9 p.m. Thanksgiving night. And it works: last year the National Retail Federation found that 24% of Black Friday shoppers got started on Thanksgiving.

"They have to keep up with one another," said Paul Poole, who was doing some early holiday shopping Tuesday at Atlantic Station. "One store's gotta outdo the other store."

Fellow shopper Chris Marshall said, "I'm definitely a fan of shopping the night before, as opposed to getting up early."

But the employees, who have to work those shifts, are not fans. An employee at Target wrote a petition that now has more than 190,000 signatures, asking the mega-store to "give Thanksgiving back to families and not open on Thanksgiving evening."

A similar petition, with more than 200,000 signatures, circulated last year when Target planned to open on midnight; that petition didn't work.